1. Field of the Invention
The invention is directed to a process for the production of stainless steel of the ferritic AISI 4xx group of steels, particularly the AISI 430 group of steels, based on liquid pig iron and FeCr solids.
2. Description of the Prior Art
The use of an AOD converter for producing special steels is already known. For example, WO 02/075003 describes a monitoring method based on a continuous measurement of waste gas in combination with a computer and a dynamic model for controlling the required blow rates for oxygen and inert gas and material additions. EP 1 310 573 A2 discloses a process for the production of a molten metal, particularly for refining a molten metal for the production of, e.g., alloyed stainless steel or special steel in an AOD converter. This process is based on a computational technique which proceeds in accordance with a process model and controls the smelting installation. The process model describes the behavior for at least one variable process parameter between an actual process quantity, a correcting variable and a final process quantity. By way of example, the process sequence for the production of a steel of AISI 304 grade is described.
Conventionally, stainless steels of the ferritic AISI 4xx group of steels are principally produced in EAF from typical scrap and are then alloyed and decarburized in addition in the AOD converter. In order to make use of pig iron for this application, pig iron that has been pretreated in a steel plant is mixed with melted down scrap and alloy in a ladle outside the furnace and is then charged into the converter.
Proceeding from this prior art, it is the object of the invention to make use of the known AOD technology for directly charging pig iron and after-alloy into the converter for the production of stainless steel of the ferritic AISI 4xx group of steels, particularly the AISI 430 group of steels.